[PATCH] iio: sx9310: Fix write_.._debounce()

[Gwendal Grignou <gwendal@chromium.org>]

Check input to be sure it matches Semtech sx9310 specification and
can fit into debounce register.
Compare argument writen to thresh_.._period with read from same
sysfs attribute:

Before:                   Afer:
write   |  read           write   |  read
-1      |     8           -1 fails: -EINVAL
0       |     8           0       |     0
1       |     0           1       |     0
2..15   |  2^log2(N)      2..15   |  2^log2(N)
16      |     0           >= 16 fails: -EINVAL

Fixes: 1b6872015f0b ("iio: sx9310: Support setting debounce values")
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Cc: stable@vger.kernel.org
---
 drivers/iio/proximity/sx9310.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/proximity/sx9310.c b/drivers/iio/proximity/sx9310.c
index 578d8841c5398..e5a756f4afa2b 100644
--- a/drivers/iio/proximity/sx9310.c
+++ b/drivers/iio/proximity/sx9310.c
@@ -764,7 +764,11 @@ static int sx9310_write_far_debounce(struct sx9310_data *data, int val)
 	int ret;
 	unsigned int regval;
 
-	val = ilog2(val);
+	if (val > 0)
+		val = ilog2(val);
+	if (!FIELD_FIT(SX9310_REG_PROX_CTRL10_FAR_DEBOUNCE_MASK, val))
+		return -EINVAL;
+
 	regval = FIELD_PREP(SX9310_REG_PROX_CTRL10_FAR_DEBOUNCE_MASK, val);
 
 	mutex_lock(&data->mutex);
@@ -781,7 +785,11 @@ static int sx9310_write_close_debounce(struct sx9310_data *data, int val)
 	int ret;
 	unsigned int regval;
 
-	val = ilog2(val);
+	if (val > 0)
+		val = ilog2(val);
+	if (!FIELD_FIT(SX9310_REG_PROX_CTRL10_CLOSE_DEBOUNCE_MASK, val))
+		return -EINVAL;
+
 	regval = FIELD_PREP(SX9310_REG_PROX_CTRL10_CLOSE_DEBOUNCE_MASK, val);
 
 	mutex_lock(&data->mutex);
-- 
2.31.0.291.g576ba9dcdaf-goog